What is the primary function of sensory receptors?
Provide information about the external and internal environments by responding to stimuli and conveying signals to the CNS.
What does the term 'transducer' mean in sensory physiology?
A receptor that converts stimulus energy into electrical energy.
How do sensory receptors convey signals to the CNS?
By generating electrical signals (action potentials) that are transmitted to the CNS via sensory neurons.
What is a receptive field?
The distribution area of the endings of a sensory neuron.
How does receptive field size affect stimulus localization?
Smaller receptive fields allow more precise stimulus localization.
What must occur for a sensation to enter conscious awareness?
Signals must reach the cerebral cortex to become sensations.
Do all sensory inputs reach conscious awareness?
No; only a fraction of stimuli result in sensations while much input is processed elsewhere.
Give an example of sensory input that is processed without conscious awareness.
Blood pressure signals relayed to the brainstem, initiating responses without conscious awareness.
What information about a stimulus do receptors provide to the CNS?
Modality, location, intensity, and duration of the stimulus.
What are modality-gated channels?
Receptor membrane channels that respond to the receptor's specific type of stimulus.
Do sensory receptors have a resting membrane potential?
Yes, receptors have a resting membrane potential.
What determines how the brain interprets the type of sensory stimulus (modality)?
The labeled line: signals from specific nerves are interpreted as particular modalities (e.g., optic nerve → vision).
List common forms of sensory information mentioned.
Does each receptor type respond to multiple stimulus types equally?
No; each receptor type responds best to a particular type of stimulus (e.g., light for eye receptors).
What determines the location of a sensory stimulus?
The location of stimulus is determined by which receptive field is active.
What does the postcentral gyrus contain related to sensation?
The postcentral gyrus has a body map represented by the homunculus.
How does receptor adaptation affect perception?
Receptor adaptation helps determine stimulus duration by decreased sensitivity to continuous stimulus.
How do tonic receptors respond to a continuous stimulus?
Tonic receptors show limited adaptation and respond continuously.
Give two examples of tonic receptors mentioned in the text.
How do phasic receptors respond to stimuli?
Phasic receptors adapt rapidly and only respond to new stimuli.
What example of phasic receptors is given in the text?
Pressure receptors are an example of phasic receptors.
What are the two main categories of sensory receptors by distribution?
What are somatic sensory receptors and where are they found?
Somatic sensory receptors are tactile receptors of skin and mucous membranes and proprioceptors of joints, muscles, and tendons.
What do visceral sensory receptors monitor and where are they found?
Visceral sensory receptors are found in walls of internal organs and monitor stretch, chemical environment, temperature, and pain.
Where are special sense receptors located and which senses do they serve?
Special sense receptors are in complex sense organs of the head and serve olfaction, gustation, vision, audition, and equilibrium.
Name the three receptor categories by stimulus origin.
What do exteroceptors detect and where are they located?
Exteroceptors detect stimuli from the external environment and are in skin, mucous membranes, and special sense receptors.
What do interoceptors detect?
Interoceptors detect stimuli from internal organs and monitor the internal environment.
What do proprioceptors detect and where are they found?
Proprioceptors detect body and limb movements and are somatosensory receptors of muscles, tendons, and joints.
What are the five receptor types by modality of stimulus?
What do chemoreceptors detect and give examples of external and internal targets?
Chemoreceptors detect chemicals dissolved in fluid; examples: smell of food (external) and oxygen levels in blood (internal).
Where are thermoreceptors located according to the text?
Thermoreceptors are located in the skin and hypothalamus.
What do photoreceptors detect and where are they found?
Photoreceptors detect changes in light intensity, color, and movement in the retina of the eye.
What stimuli do mechanoreceptors detect and what functions do they serve?
Mechanoreceptors detect distortion of the cell membrane and include touch, pressure, vibration, and stretch receptors; they function as baroreceptors, proprioceptors, tactile receptors, and inner ear specialized receptors.
What do nociceptors detect and how are somatic and visceral nociceptors different?
Nociceptors detect painful stimuli. Somatic nociceptors detect chemical, heat, or mechanical damage to body surface or skeletal muscles; visceral nociceptors detect internal organ damage.
What are tactile receptors?
What defines unencapsulated tactile receptors?
Describe free nerve endings.
What do root hair plexuses detect and how do they adapt?
What are tactile discs (Merkel-related) and their function?
What characterizes encapsulated tactile receptors?
State the function and adaptation of lamellated (Pacinian) corpuscles.
What do tactile (Meissner) corpuscles detect and where are they found?
What is the role and adaptation of bulbous (Ruffini) corpuscles?
What are end (Krause) bulbs sensitive to and how do they adapt?
Define olfaction.
How are odorants detected in the nose?
What kinds of information does olfaction provide?
How many different odors can humans distinguish as stated?
What is the primary sensory receptor organ for smell in the nasal cavity?
Name the three cell types found in the olfactory epithelium.
What is the role of basal cells in the olfactory epithelium?
How does aging affect olfactory receptor cells?
What structures are contained in the lamina propria beneath the olfactory epithelium?
What is the function of olfactory (Bowman) glands?
Describe the structure of an olfactory receptor cell.
Where are olfactory hairs and what do they contain?
Trace the path of olfactory receptor cell axons from the nasal cavity to the brain.
Where do olfactory nerve fibers synapse within the olfactory bulb?
To which brain regions do olfactory tracts project?
How does the olfactory pathway differ from other sensory pathways regarding the thalamus?
What initiates an olfactory receptor cell's electrical response when an odorant is present?
Describe the intracellular signaling sequence in an olfactory receptor cell after odorant binding.
What CNS areas receive secondary olfactory neuron signals and what are their roles?
What is gustation?
Gustation is the sense of taste; detection of tastants.
What are gustatory cells?
Gustatory cells are chemoreceptor receptor cells within taste buds that detect tastants.
Name the four cell types or structures found in a taste bud.
How do tastants reach and stimulate gustatory microvilli?
Tastants dissolve in saliva, reach the taste pore, and stimulate the gustatory microvillus often extending to the tongue surface.
List the five basic taste sensations.
Which tastants produce sweet, bitter, and umami sensations and how do they transduce signals?
Sweet, bitter, and umami are produced by molecules that bind membrane receptors, activate a G protein, form a second messenger, and cause cell depolarization.
How are salt and sour taste transduced in gustatory cells?
Salt and sour tastants are ions that depolarize the gustatory cell directly.
What happens after a gustatory cell depolarizes?
A depolarized gustatory cell releases neurotransmitter that stimulates a primary neuron in CN VII or CN IX.
Which papillae contain most of the taste buds and where are they located?
Vallate (circumvallate) papillae contain most of the taste buds and are in a row of 10 to 12 along the posterior dorsal tongue surface.
Which papillae have no taste buds and what is their function?
Filiform papillae have no taste buds; they are short, spiked, located on the anterior two-thirds of the tongue surface, and help manipulate food.
Where are fungiform and foliate papillae located and what is a key feature of each?
How do sensory neurons from the tongue project in the gustatory pathway?
Sensory neurons connect to multiple gustatory cells in the tongue and project to the medulla.
Which cranial nerve carries taste sensation from the anterior part of the tongue?
Which cranial nerve carries taste sensation from the posterior two-thirds of the tongue?
Where does the primary gustatory neuron bring its signal in the brainstem?
What medullary responses are triggered by gustatory input?
After medullary processing, where do secondary gustatory neurons send signals?
To which cortical area do tertiary gustatory neurons project for conscious taste?
How is taste integrated with other senses?
What happens to perception of food taste when olfaction is blocked?
What is the role of photoreceptors in vision?
What causes refraction of light in the eye?
What does the refractive index represent?
Describe the eye's resting focus for objects 20 feet away or farther.
Describe the near response when focusing on objects closer than 20 feet.
What visual problem results from unequal strength of extrinsic eye muscles?
What is emmetropia?
What is hyperopia (farsightedness)?
Trouble seeing up close because the eyeball is too short; only convergent rays from distant points are brought to focus.
How is hyperopia corrected?
With a convex lens.
What is myopia (near-sightedness)?
Trouble seeing faraway objects because the eyeball is too long; only rays close to the eye focus on the retina.
How is myopia corrected?
With a concave lens.
What causes astigmatism?
Unequal focusing due to unequal curvatures in one or more refractive surfaces.
What is presbyopia and one common effect?
Age-related change where the lens is less able to become spherical; reading close-up words becomes difficult.
How can presbyopia be corrected or treated?
Corrective convex lens or various surgical techniques.
What is phototransduction?
Converting light to electrical signals performed by photoreceptor cells (rods and cones).
Name the main parts of a photoreceptor cell from outer to inner.
What are two key features of the outer segment discs in photoreceptors?
They contain photopigments that absorb light and are continually replaced.
How do rods differ from cones in sensitivity and distribution?
Rods are longer, narrower, more numerous, highly sensitive to dim light, and concentrated in the retinal periphery.
How does the neural wiring of rods affect vision?
Many rods converge on fewer bipolar and ganglion cells, producing high sensitivity in dim light but a blurry image.
What are three key features of cones related to acuity and light?
Concentrated at the fovea centralis; activated by high-intensity light; allow color vision.
How does the one-to-one wiring of cones affect visual acuity?
One-to-one relationships with bipolar and ganglion cells yield a sharp image but only in bright light.
What are photopigments made of?
An opsin protein bound to light-absorbing retinal (made from Vitamin A).
Where are photopigments located in photoreceptors?
Within membranes of the outer segments of rods and cones.
Which neurotransmitter is stored in photoreceptor synaptic terminals?
Glutamate.
What photopigment do rods contain?
How many cone types are there and what differs between them?
Which cone type detects short wavelengths (blue)?
Which cone type detects intermediate wavelengths (green)?
Which cone type best detects long wavelengths (red)?
What is the primary cause of the most common forms of color blindness?
Describe the basic retinal neural pathway from photoreceptors to the brain.
What happens to medial and lateral optic nerve axons at the optic chiasm?
Where do most optic tract axons project after the optic chiasm, and where do thalamic neurons send axons?
What role do superior colliculi receive from some optic tract axons?
What is 'visual field' in vision physiology?
How does stereoscopic vision arise from visual fields?
What three factors determine visual acuity?
What does a 20/20 visual acuity rating mean?
What does a 20/200 visual acuity rating indicate?
What reflexes do the pretectal nuclei coordinate?
The pretectal nuclei coordinate the pupillary reflex and lens accommodation reflex.
What is special about the ganglion cells that project to the pretectal nuclei?
They are directly photoresponsive and contain the melanopsin pigment.
What two special senses are provided by the inner ear?
Hearing and equilibrium.
What head movements or forces do equilibrium sensations monitor?
What is the spiral organ and where is it located?
The spiral organ is the sensory structure for hearing and is located within the cochlear duct.
Describe the hair cell arrangement in the spiral organ.
There is a single row of inner hair cells and three rows of outer hair cells; hair cells have many stereocilia and one kinocilium at their apex.
Outline the pathway from sound wave to nerve signal in the ear.
How do cochlear hair cells depolarize when stimulated?
Basilar membrane movement tilts hair cell tips, tip links pull open ion channels, allowing K+ from endolymph to enter and depolarize the hair cell.
What happens after a hair cell depolarizes in the cochlea?
The hair cell releases more neurotransmitter from its base, exciting the sensory neuron which can fire action potentials.
What happens to pressure after it passes through the cochlear duct?
Pressure is transmitted to the scala tympani and absorbed by the round window.
How is sound perceived?
Sound is the perception of pressure waves established from vibrating objects.
What determines the pitch of a sound?
The frequency of the vibrating object (rate of vibration in Hertz).
What is the human audible frequency range?
How does the basilar membrane encode high- versus low-frequency sounds?
What physical property of a sound wave determines loudness?
The amplitude of the wave (degree of molecular compression).
How do louder sounds affect the basilar membrane and nerve signals?
Louder sounds cause larger basilar membrane movements, producing a faster rate of nerve signals and more stimulated cells.
What unit measures loudness and what is the hearing threshold?
How does sound energy change with decibel increases?
Sound energy increases ten times for every 10 dB increase.
What is the sequence of main relay stations in the auditory pathway from cochlea to cortex?
What role does the inferior colliculus play in hearing?
It coordinates head orienting reflexes to sounds.
What functions are attributed to the superior olivary nucleus?
What structures make up the vestibular apparatus that monitor head position?
Which vestibular structures detect static equilibrium and linear acceleration?
The utricle and saccule detect static equilibrium and linear acceleration.
Which vestibular structures detect angular acceleration?
The semicircular ducts detect angular acceleration.
What is the macula and where is it located?
The macula is the receptor for static equilibrium and linear acceleration, located in the utricle and saccule.
Describe the key cellular components of the macula's receptor epithelium.
It is composed of hair cells and supporting cells; hair cells have stereocilia and one kinocilium projecting into an otolithic membrane.
What are otoliths and where are they found?
Otoliths are calcium carbonate crystals that cover the otolithic membrane in the utricle and saccule.
What happens to the otolithic membrane and stereocilia when the head tilts?
The head tilt shifts the otolithic membrane and bends the stereocilia.
What is the effect on a hair cell when its stereocilia are bent toward the kinocilium?
The hair cell depolarizes and increases its transmitter release.
How does increased transmitter release from depolarized hair cells affect the vestibular nerve?
It increases impulse frequency on the vestibular part of CN VIII.
What is the response when stereocilia bend away from the kinocilium?
An opposite reaction occurs: the hair cell hyperpolarizes and transmitter release decreases.
What special structure is located at the base of each semicircular canal?
The ampulla is the region at the base of each semicircular canal.
What sensory structure does the ampulla contain?
The ampulla contains the crista ampullaris with hair cells and support cells.
Where are the stereocilia and kinocilia of ampullary hair cells embedded?
They are embedded in a gelatinous structure called the cupula.
What causes the cupula to bend during head rotation?
When the head rotates, endolymph pushes against the cupula, causing it to bend.
How does bending of the cupula affect hair cell voltage?
Cupula bending deflects stereocilia and changes hair cell voltage: toward kinocilium depolarizes, away hyperpolarizes.
Where do signals from the maculae or crista ampullaris travel first?
They are conveyed by the vestibular branch of CN VIII.
To which two brain regions do vestibular axons terminate?
Vestibular axons terminate in the vestibular nuclei or the cerebellum.
What role do the vestibular nuclei in the superior medulla play?
They help control reflexive eye movements and balance.
What function does the cerebellum serve in vestibular processing?
The cerebellum helps coordinate balance and muscle tone.
After the vestibular nuclei and cerebellum process vestibular signals, where are they sent next?
They send signals to the thalamus.
What is the thalamus's role in vestibular pathways?
The thalamus relays vestibular information to the cerebral cortex for awareness of body position.
What is the primary function of sensory receptors?
Provide information about the external and internal environments by responding to stimuli and conveying signals to the CNS.
What does the term 'transducer' mean in sensory physiology?
A receptor that converts stimulus energy into electrical energy.
How do sensory receptors convey signals to the CNS?
By generating electrical signals (action potentials) that are transmitted to the CNS via sensory neurons.
How does receptive field size affect stimulus localization?
Smaller receptive fields allow more precise stimulus localization.
What must occur for a sensation to enter conscious awareness?
Signals must reach the cerebral cortex to become sensations.
Do all sensory inputs reach conscious awareness?
No; only a fraction of stimuli result in sensations while much input is processed elsewhere.
Give an example of sensory input that is processed without conscious awareness.
Blood pressure signals relayed to the brainstem, initiating responses without conscious awareness.
What information about a stimulus do receptors provide to the CNS?
Modality, location, intensity, and duration of the stimulus.
What are modality-gated channels?
Receptor membrane channels that respond to the receptor's specific type of stimulus.
Do sensory receptors have a resting membrane potential?
Yes, receptors have a resting membrane potential.
What determines how the brain interprets the type of sensory stimulus (modality)?
The labeled line: signals from specific nerves are interpreted as particular modalities (e.g., optic nerve → vision).
Does each receptor type respond to multiple stimulus types equally?
No; each receptor type responds best to a particular type of stimulus (e.g., light for eye receptors).
What determines the location of a sensory stimulus?
The location of stimulus is determined by which receptive field is active.
What does the postcentral gyrus contain related to sensation?
The postcentral gyrus has a body map represented by the homunculus.
How does receptor adaptation affect perception?
Receptor adaptation helps determine stimulus duration by decreased sensitivity to continuous stimulus.
How do tonic receptors respond to a continuous stimulus?
Tonic receptors show limited adaptation and respond continuously.
Give two examples of tonic receptors mentioned in the text.
How do phasic receptors respond to stimuli?
Phasic receptors adapt rapidly and only respond to new stimuli.
What example of phasic receptors is given in the text?
Pressure receptors are an example of phasic receptors.
What are the two main categories of sensory receptors by distribution?
What are somatic sensory receptors and where are they found?
Somatic sensory receptors are tactile receptors of skin and mucous membranes and proprioceptors of joints, muscles, and tendons.
What do visceral sensory receptors monitor and where are they found?
Visceral sensory receptors are found in walls of internal organs and monitor stretch, chemical environment, temperature, and pain.
Where are special sense receptors located and which senses do they serve?
Special sense receptors are in complex sense organs of the head and serve olfaction, gustation, vision, audition, and equilibrium.
What do exteroceptors detect and where are they located?
Exteroceptors detect stimuli from the external environment and are in skin, mucous membranes, and special sense receptors.
What do interoceptors detect?
Interoceptors detect stimuli from internal organs and monitor the internal environment.
What do proprioceptors detect and where are they found?
Proprioceptors detect body and limb movements and are somatosensory receptors of muscles, tendons, and joints.
What are the five receptor types by modality of stimulus?
What do chemoreceptors detect and give examples of external and internal targets?
Chemoreceptors detect chemicals dissolved in fluid; examples: smell of food (external) and oxygen levels in blood (internal).
Where are thermoreceptors located according to the text?
Thermoreceptors are located in the skin and hypothalamus.
What do photoreceptors detect and where are they found?
Photoreceptors detect changes in light intensity, color, and movement in the retina of the eye.
What stimuli do mechanoreceptors detect and what functions do they serve?
Mechanoreceptors detect distortion of the cell membrane and include touch, pressure, vibration, and stretch receptors; they function as baroreceptors, proprioceptors, tactile receptors, and inner ear specialized receptors.
What do nociceptors detect and how are somatic and visceral nociceptors different?
Nociceptors detect painful stimuli. Somatic nociceptors detect chemical, heat, or mechanical damage to body surface or skeletal muscles; visceral nociceptors detect internal organ damage.
What are tactile receptors?
What defines unencapsulated tactile receptors?
Describe free nerve endings.
What are tactile discs (Merkel-related) and their function?
What characterizes encapsulated tactile receptors?
State the function and adaptation of lamellated (Pacinian) corpuscles.
What do tactile (Meissner) corpuscles detect and where are they found?
What is the role and adaptation of bulbous (Ruffini) corpuscles?
What are end (Krause) bulbs sensitive to and how do they adapt?
How are odorants detected in the nose?
How many different odors can humans distinguish as stated?
Name the three cell types found in the olfactory epithelium.
What is the role of basal cells in the olfactory epithelium?
How does aging affect olfactory receptor cells?
What structures are contained in the lamina propria beneath the olfactory epithelium?
What is the function of olfactory (Bowman) glands?
Describe the structure of an olfactory receptor cell.
Where are olfactory hairs and what do they contain?
Trace the path of olfactory receptor cell axons from the nasal cavity to the brain.
Where do olfactory nerve fibers synapse within the olfactory bulb?
To which brain regions do olfactory tracts project?
How does the olfactory pathway differ from other sensory pathways regarding the thalamus?
What initiates an olfactory receptor cell's electrical response when an odorant is present?
Describe the intracellular signaling sequence in an olfactory receptor cell after odorant binding.
What CNS areas receive secondary olfactory neuron signals and what are their roles?
What are gustatory cells?
Gustatory cells are chemoreceptor receptor cells within taste buds that detect tastants.
Name the four cell types or structures found in a taste bud.
How do tastants reach and stimulate gustatory microvilli?
Tastants dissolve in saliva, reach the taste pore, and stimulate the gustatory microvillus often extending to the tongue surface.
Which tastants produce sweet, bitter, and umami sensations and how do they transduce signals?
Sweet, bitter, and umami are produced by molecules that bind membrane receptors, activate a G protein, form a second messenger, and cause cell depolarization.
How are salt and sour taste transduced in gustatory cells?
Salt and sour tastants are ions that depolarize the gustatory cell directly.
What happens after a gustatory cell depolarizes?
A depolarized gustatory cell releases neurotransmitter that stimulates a primary neuron in CN VII or CN IX.
Which papillae contain most of the taste buds and where are they located?
Vallate (circumvallate) papillae contain most of the taste buds and are in a row of 10 to 12 along the posterior dorsal tongue surface.
Which papillae have no taste buds and what is their function?
Filiform papillae have no taste buds; they are short, spiked, located on the anterior two-thirds of the tongue surface, and help manipulate food.
Where are fungiform and foliate papillae located and what is a key feature of each?
How do sensory neurons from the tongue project in the gustatory pathway?
Sensory neurons connect to multiple gustatory cells in the tongue and project to the medulla.
Which cranial nerve carries taste sensation from the anterior part of the tongue?
Which cranial nerve carries taste sensation from the posterior two-thirds of the tongue?
Where does the primary gustatory neuron bring its signal in the brainstem?
What medullary responses are triggered by gustatory input?
To which cortical area do tertiary gustatory neurons project for conscious taste?
How is taste integrated with other senses?
What happens to perception of food taste when olfaction is blocked?
What causes refraction of light in the eye?
Describe the eye's resting focus for objects 20 feet away or farther.
Describe the near response when focusing on objects closer than 20 feet.
What visual problem results from unequal strength of extrinsic eye muscles?
What is hyperopia (farsightedness)?
Trouble seeing up close because the eyeball is too short; only convergent rays from distant points are brought to focus.
What is myopia (near-sightedness)?
Trouble seeing faraway objects because the eyeball is too long; only rays close to the eye focus on the retina.
What causes astigmatism?
Unequal focusing due to unequal curvatures in one or more refractive surfaces.
What is presbyopia and one common effect?
Age-related change where the lens is less able to become spherical; reading close-up words becomes difficult.
What is phototransduction?
Converting light to electrical signals performed by photoreceptor cells (rods and cones).
Name the main parts of a photoreceptor cell from outer to inner.
What are two key features of the outer segment discs in photoreceptors?
They contain photopigments that absorb light and are continually replaced.
How do rods differ from cones in sensitivity and distribution?
Rods are longer, narrower, more numerous, highly sensitive to dim light, and concentrated in the retinal periphery.
How does the neural wiring of rods affect vision?
Many rods converge on fewer bipolar and ganglion cells, producing high sensitivity in dim light but a blurry image.
What are three key features of cones related to acuity and light?
Concentrated at the fovea centralis; activated by high-intensity light; allow color vision.
How does the one-to-one wiring of cones affect visual acuity?
One-to-one relationships with bipolar and ganglion cells yield a sharp image but only in bright light.
What are photopigments made of?
An opsin protein bound to light-absorbing retinal (made from Vitamin A).
Where are photopigments located in photoreceptors?
Within membranes of the outer segments of rods and cones.
How many cone types are there and what differs between them?
Which cone type detects intermediate wavelengths (green)?
What is the primary cause of the most common forms of color blindness?
Describe the basic retinal neural pathway from photoreceptors to the brain.
What happens to medial and lateral optic nerve axons at the optic chiasm?
Where do most optic tract axons project after the optic chiasm, and where do thalamic neurons send axons?
What role do superior colliculi receive from some optic tract axons?
What is 'visual field' in vision physiology?
How does stereoscopic vision arise from visual fields?
What three factors determine visual acuity?
What does a 20/20 visual acuity rating mean?
What does a 20/200 visual acuity rating indicate?
What reflexes do the pretectal nuclei coordinate?
The pretectal nuclei coordinate the pupillary reflex and lens accommodation reflex.
What is special about the ganglion cells that project to the pretectal nuclei?
They are directly photoresponsive and contain the melanopsin pigment.
What head movements or forces do equilibrium sensations monitor?
What is the spiral organ and where is it located?
The spiral organ is the sensory structure for hearing and is located within the cochlear duct.
Describe the hair cell arrangement in the spiral organ.
There is a single row of inner hair cells and three rows of outer hair cells; hair cells have many stereocilia and one kinocilium at their apex.
Outline the pathway from sound wave to nerve signal in the ear.
How do cochlear hair cells depolarize when stimulated?
Basilar membrane movement tilts hair cell tips, tip links pull open ion channels, allowing K+ from endolymph to enter and depolarize the hair cell.
What happens after a hair cell depolarizes in the cochlea?
The hair cell releases more neurotransmitter from its base, exciting the sensory neuron which can fire action potentials.
What happens to pressure after it passes through the cochlear duct?
Pressure is transmitted to the scala tympani and absorbed by the round window.
How is sound perceived?
Sound is the perception of pressure waves established from vibrating objects.
What determines the pitch of a sound?
The frequency of the vibrating object (rate of vibration in Hertz).
How does the basilar membrane encode high- versus low-frequency sounds?
What physical property of a sound wave determines loudness?
The amplitude of the wave (degree of molecular compression).
How do louder sounds affect the basilar membrane and nerve signals?
Louder sounds cause larger basilar membrane movements, producing a faster rate of nerve signals and more stimulated cells.
What unit measures loudness and what is the hearing threshold?
How does sound energy change with decibel increases?
Sound energy increases ten times for every 10 dB increase.
What is the sequence of main relay stations in the auditory pathway from cochlea to cortex?
What role does the inferior colliculus play in hearing?
It coordinates head orienting reflexes to sounds.
What functions are attributed to the superior olivary nucleus?
What structures make up the vestibular apparatus that monitor head position?
Which vestibular structures detect static equilibrium and linear acceleration?
The utricle and saccule detect static equilibrium and linear acceleration.
Which vestibular structures detect angular acceleration?
The semicircular ducts detect angular acceleration.
What is the macula and where is it located?
The macula is the receptor for static equilibrium and linear acceleration, located in the utricle and saccule.
Describe the key cellular components of the macula's receptor epithelium.
It is composed of hair cells and supporting cells; hair cells have stereocilia and one kinocilium projecting into an otolithic membrane.
What are otoliths and where are they found?
Otoliths are calcium carbonate crystals that cover the otolithic membrane in the utricle and saccule.
What happens to the otolithic membrane and stereocilia when the head tilts?
The head tilt shifts the otolithic membrane and bends the stereocilia.
What is the effect on a hair cell when its stereocilia are bent toward the kinocilium?
The hair cell depolarizes and increases its transmitter release.
How does increased transmitter release from depolarized hair cells affect the vestibular nerve?
It increases impulse frequency on the vestibular part of CN VIII.
What is the response when stereocilia bend away from the kinocilium?
An opposite reaction occurs: the hair cell hyperpolarizes and transmitter release decreases.
What special structure is located at the base of each semicircular canal?
The ampulla is the region at the base of each semicircular canal.
What sensory structure does the ampulla contain?
The ampulla contains the crista ampullaris with hair cells and support cells.
Where are the stereocilia and kinocilia of ampullary hair cells embedded?
They are embedded in a gelatinous structure called the cupula.
What causes the cupula to bend during head rotation?
When the head rotates, endolymph pushes against the cupula, causing it to bend.
How does bending of the cupula affect hair cell voltage?
Cupula bending deflects stereocilia and changes hair cell voltage: toward kinocilium depolarizes, away hyperpolarizes.
Where do signals from the maculae or crista ampullaris travel first?
They are conveyed by the vestibular branch of CN VIII.
To which two brain regions do vestibular axons terminate?
Vestibular axons terminate in the vestibular nuclei or the cerebellum.
What role do the vestibular nuclei in the superior medulla play?
They help control reflexive eye movements and balance.
What function does the cerebellum serve in vestibular processing?
The cerebellum helps coordinate balance and muscle tone.
After the vestibular nuclei and cerebellum process vestibular signals, where are they sent next?
They send signals to the thalamus.
What is the thalamus's role in vestibular pathways?
The thalamus relays vestibular information to the cerebral cortex for awareness of body position.
Study tip: Focus first on receptor types and where they send signals (which cranial/spinal nerves and primary CNS targets), then learn distinctive transduction mechanisms (G-protein vs ion-channel mediated) and the special organ structures that implement them.
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